Silk screen stretcher



July 22, 1958 E'LISE. F. HARMON SILK SCREEN STRETGHER Filed Nov. 15.1953 INVENTOR. E'liae F1 Hum-nun BY #5 a 60 Aux) ATTO/ENE Y5 tried inthe past. These to tension the silk fabric 8.

UnitedStates PatentO 2,844,172? SILK SCREEN STRETCHER.

Elise F. Harmon, New Bedford, Massi,assignortd the United States ofAmerica as represented by the Secre- The invinienueseribeir hererir mabe manufactured and used by or for the Government for governmentalpurposes without the payment to me of any royalty thereon.

This invention relates to a mechanism for stretching fabric materials toattain uniformity of tautness.

An object of the invention is to provide a device which will uniformlytension, in all directions, the entire body of a sheet of fabric.

Another object of the invention is to provide a device which will, inmass production, stretch fabric screens for use in printing electricalcircuits or the like.

A further object of the invention is to provide a fabric stretchingdevice which is simple in construction and effective in operation.

Other objects and advantages will be apparent from the followingdetailed description and the accompanying drawings, in which the singlefigure is a perspective view with parts broken away to show the interiorstructure, and showing a silk fabric screen being stretched.

In the art of printing the silk-screen process is well known. Itconsists of applying a tightly stretched silk screen to the surface tobe imprinted, portions screen being masked to prevent the passage of inkor paint. The screen is fed with a supply of ink or paint,

and this material is then pressed through the screen by means of aroller. The screen is then raised, leaving ink or paint on the portionof the surface which isunmasked.

Various methods of stretching the screens have been have been more orless clumsy and time consuming. In the production of printed circuitsand components greater uniformity of tautness over the surface of asingle screen is required than can be obtained by the usual methods, andgreater uniformity is of such I also needed between screens used toproduce the same circuits, in mass production.

To produce screens which will individually be uniformly taut, and toproduce a plurality of screens which will all be of the same tautness, Ihave invented the silk screen stretcher herein disclosed.

Referring now to the drawing, the reference character 5 indicates a baseplate. Secured to the base plate, preferably near each corner thereof,are posts 6. The posts extend upwardly from the base plate 5 and supporta table 7 on their upper ends. A single sheet of silk fabric 8, shownoutlined in dotted lines, is spread smoothly over the table top andsecured to the edges thereof by a clamping frame 9. Screw clamps 10, inany required number hold the clamping frame and the silk fabric securelyto the table 7. Centrally thereof and uniformly spaced from the sideedges of the table there is formed an opening 11, through which avertically movable platform 12 is raised Centrally of the base plate 5and the platform 12 there is positioned a lifting jack 13. Ascrew-threaded jack screw 14 is fixed to the platform 12 at its upperend and extends downwardly into the jack 13. In screw-threadedengagement with the jack screw 14 and rotatable there- 2,844,172Patented July 22, 1958 v 2 around is-a nut 15'. 1 Formed in' the sidesurface of the jack" screw andextending longitudinally thereof is a keyslot 16 'for' 'slidably; receivinga ke'y;17." The key is formed on a"collar 18' 'surroundin'g the jack s'crew andis secured by screws -19*toa sub-table 20, which is supported on the posts 6 inter'mediatethe tableand the base plate 5n Positioned 'ontheplatfo" 12- is aremovablerectangular frame 21 to which wo-stretched fabric 'is finallysecuredto'-- insure a *properlvstretched"'silkscreen. A 'rounded molding22; is 'seci i'e'dto the platform-12 outside the frame so that thefabric does notencounter any sharp edges. Thus the moldir'ig' 22assthe-'double function of protecting delicatefabric from damage whenstretched, and also retaining-theframe; 21 in po'sitio'n.-- When not usethe platform 12" lison' sub table-20i -Whe'n'-th'e desired tension hasbeen obtained, a frame 23 is placed over the silk fabric on the screenframe 21 and tacked tightly in place.

The operation of the invention is as follows:

The platform 12 1s lowered by rotating the nut 15 on "ice i the jack 13until the platform rests on the sub-table 20 or until the top surface ofthe screen frame 21 is slightly below the top surface of the table 7. Asheet of silk fabric 8 which is to form a screen is laid smoothly on thetable 7 above the frame 21. The clamping frame 9 is placed on top of thesilk fabric and firmly clamped in place by any number of screw clamps 10as are found necessary. Thereafter the nut 15 is rotated in the oppositedirection to raise the platform 12, the screen frame 21 and the bearingmolding 22 until the silk has attained the desired degree of tautness.When the desired tension has been obtained the cardboard frame 23 isplaced on the screen frame over the silk fabric and tacked tightly inplace. The nut 9 is then rotated to lower the jack screw 14 and theplatform 12 until tension on the fabric is relieved. Thereafter theclamps 10 and the clamping frame 9 are removed, and the silk is cutclose to the outside of the frame 21. A silk screen is then ready to beused.

While I have disclosed a form of the invention presently preferred byme, various changes and modifications will occur to those skilled in theart after a study of the present disclosure. Hence the disclosure is tobe taken in an illustrative rather than a limiting sense; and it is mydesire and intention to reserve all modifications falling within thescope of the subjoined claim.

Having now fully disclosed the invention, and desire to secure byLetters Patent is:

A mechanism for stretching a sheet of fabric material comprising, a baseplate having a rectangular configuration, a plurality of posts extendingupwardly from and adjacent each corner of said base plate, a supportingtable having an upper planar supporting surface and secured to the upperends of said posts, said supporting table having the same externaldimensions as said base plate, a detachable rectangular clamping framereceived on said supporting surface, said clamping frame having the sameexternal dimensions as said supporting lower planar gripping surface forgripping said material. between said frame and said supporting surfaceon said table, a plurality of screw clamps for clamping said clampingframe on said supporting table, there being a centrally disposedrectangular opening in said supporting table and spaced uniformly fromthe inner edges of said clamping frame when in clamping position wherebysaid supporting surface provides a rectangularly disposed planarsupporting surface between said opening and said clamping surface, meansfor imposing a predetermined stress on said material including a jack,comprising a tubular base secured centrally on said base plate, a jackscrew having a longitudinal slot therein received in said tubular base,

what I claim table and provided with a an operating nut carried by saidtubular base and threadably engaging said jack screw, a rectangularplatform secured on said jack screw, said platform having a peripheraldimension slightly less than said opening in said supporting table fortranslation therethrough, a rectangularly disposed rounded molding fixedon said platform and having external dimensions equal to the externaldimensions of said platform, means preventing rotation of said platformduring said translation through said opening in said supporting tablecomprising a sub table having external dimensions equal tothe externaldimensions of said base plate and said supporting table, said sub tablehaving a centrally disposed opening,r eceiving said jack screw, anannular collar rigidly secured to said sub table in said centralopening, there being a key integral with said collar and normally ridingin said-slot in said jack screw, and means adapted to secureta portionof said material in stressed condition for cutting and removal from saidmechanism comprising, a detachable rectangular stretching frame havingexternal dimensions slightly less than the internal dimensions of saidrounded molding adapted to be slidably received within said roundedmolding and a rectangular clamping frame having external and internaldimensions corresponding to the external and internal dimensions of saidstretching frame and adapted to be secured over said stressed materialon said detachable rectangular fi'ame.

References Cited in the file of this patent UNITED STATES PATENTS

